QSPR Modeling of the Polarizability of Polyaromatic Hydrocarbons and Fullerenes

Abstract

Polarizability is one of the key properties determining the nonlinear optical effects of the new materials. In the current study, a quantitative structure-property relationship approach is used to model the polarizability of polyaromatic hydrocarbons (PAHs) and fullerenes. The model is derived using the data set of 40 PAHs and fullerenes and includes just one molecular descriptor, the AM1-calculated total molecular two-center exchange energy. The model is externally validated, and the obtained results are in good agreement with both the ab initio calculated and the experimental polarizabilities of these compounds. The reported quantitative structure-property relationship is a quick tool for finding an estimate of polarizability for different PAHs and fullerenes.

Qualitative behavior of cosmological models combining various matter fields

“…First, and foremost among them, is assuming a positive cosmological constant Λ in the framework of the so-called ΛCDM where cosmological constant and cold dark matter supply the largest part of the matter-energy content of the universe. Even though this model fits very well with recent astronomical observational data, there are some unresolved issues, the so-called cosmological constant problem [3,4] and coincidence problem [5], related to the tiny value of Λ and its fine tuning with today observed matter content of the universe. Another approach to handle the problem is considering the observed value of cosmological constant to be dynamically derived from some evolutionary process.…”

The Minkowski quantum vacuum does not gravitate

“…Yet, the very fact that the Minkowski vacuum does not gravitate in elementary particle physics does not solve the main cosmological constant problem. Indeed, the Higgs condensate contributes a negative energy density of order (100 GeV) 4 to the cosmological constant [3]. The energy density of dark energy is, however, of order (0.001 eV) 4 .…”

“…The energy density of dark energy is, however, of order (0.001 eV) 4 . Besides, it seems that the vacuum in quantum chromodynamics makes a contribution of order (0.3 GeV) 4 to the total vacuum energy of the Universe [4]. The former contribution may be got rid of by redefining the Higgs potential, while the latter, probably, requires novel ideas, such as [10,11], to harmonise the Standard Model with astrophysical observations.…”

“…The state |0 denotes the Minkowski vacuum of the non-interacting theory. This integral quartically diverges and, thereby, leads to the zero-point-energy problem [1][2][3][4].…”

“…Quantum fields give rise to an infinite vacuum energy density [1][2][3][4], which arises from quantum-field fluctuations taking place even in the absence of matter. Yet, assuming that semi-classical quantum field theory is reliable only up to the Planck-energy scale, the cut-off estimate yields zero-point-energy density which is finite, though, but in a notorious tension with astrophysical observations.…”